Magnetic antenna



March 14, 1961 cHlcHESTER 2,975,421

MAGNETIC ANTENNA Filed Feb. 28, 1956 F l G. 2 INVENTOR GEORGE D. CHIC HESTER M664 M'M/ ATTORNEY! U i e Stat This invention is for an improvement in antennas for radios and other electromagnetic wave translating devices, and is for an antenna utilizing permanent magnets.

In many cases antenna provided for radios, as for example automobile radios, are inefiective in certain areas due to the fact that the area may be shielded by the surrounding buildings or terrain, or for some other reason. The present invention provides an antenna which is responsive to the ground waves and therefore is eifective in areas where conventional antenna systems fail.

My invention may be more fully understood by reference to the accompanying drawing, in which:

Fig. 1 is a plan view of an antenna embodying my invention, having one of the two plates thereof removed; and

Fig. 2 is a transverse vertical section through the structure shown in Fig. 1.

Referring to the drawings, 2 designates a magnetizable metal plate, and 3 is a perforate structure extending out from the metal plate. It is here shown as a reticulated screen, but may be in the form of rods or Wires extending in various directions from the periphery of the plate 2. Actually the plate 2 may be soldered or otherwise secured to the center of the screen 3 in the manufacture of the device. On one face of the plate 2 there is a flat coil of wire, preferably fine wire having several hundred convolutions, but the size of the, coil is not critical. This coil is designated 4. At 5 and 6 are two permanent bar magnets having two like poles in confronting relation. The coil 4 is secured to one face of these magnets, and the magnets extend diametrically across the coil with the confronting ends of the magnets in closely spaced relation at the center of the coil. The

plate 2 is of an area greater than the area of the coil and magnet assembly. The assembly may be placed with the coil adjacent to the plate 2, or with the magnets adjacent the plate 2, and in either case the permanent magnets will hold the magnet and coil assembly in place, but in addition some securing medium such as a suitable cement or solder may be used to permanently fix the magnet and coil assembly on the plates.

Preferably there is a second magnetizable metal plate 7 spaced above the plate 2 and parallel therewith, the plate 7 being coextensive with the plate 2 and being held in spaced relation with the plate 2 by stand-off insulators 8, one of which is placed at each corner of the plates. The plate 7 like the plate 2 is provided with an extended accumulating surface 9 Which is coextensive with 3, and which may be formed of rods, wires, or mesh cloth, or of a wire mesh, and which is in conducting relation to the plate 7 so as to form in effect an open extension of the plate 7.

The coil 4 is provided with two leads, In some instances one lead only will be connected to an antenna circuit of a radio or other electromagnetic wave translating device, and in other cases one lead may be connected to an antenna lead wire, and the other lead from A 2,975,421 Patented Mar. 14, 1961 shielding wire around the antenna wire. This is more or less schematically illustrated in Fig. 1 where10 designates one'of the lead wires from thecoil, and 11' isthe other one. 10 is shown connected to the central conductor of a cable 12, whereas 11 is connected to stranded wire surrounding but insulated from they central conducting core of the cable.

The device as thus constructed is relatively cheap to manufacture. When it is used as the antenna for an automobile radio, it is hung from the chassis underneath the automobile, being suspended by insulated wires or other non-conducting suspension means. Being on the under side of the car it is close to the ground and therefore is especially responsive to the so-called ground waves from a transmitting station.

In operation the antenna has been successfully used for the reception of short wave, frequency modulated, and amplitude modulated signals over the normal broadcast range, and has been effective for the picking up of signals in areas and under conditions where conventional antenna systems have failed or give very unsatisfactory results.

The theory of operation or the reasons as to why the antenna gives improved reception is not known to me, but the plate 2 with its extensions 3 is larger than the magnet and coil assembly so that the fields of the magnets will be to a substantial degree returned through the plate and in order that the device have adequate area to pick up the signal without the magnet and coil being cumbersome or unnecessarily large. The placing of the magnets with like poles confronting each other has proved to be of advantage in the assembly. It gives the cumulative effect of two permanent magnets at the center of the coil, while their respective fields are deflected by their mutually repelling effect at substantially right angles to the axes of the bar magnets, so there is a sharp line across the plate where the two fields are opposed and the edges of the plate fore and aft of the magnet assembly are of like polarity. The other plate 7 with its extension end insulated from the plate 2 also functions in a manner not presently known to me, but possibly may be due to a capacity relation between this plate and the plate 2 with the magnet and coil assembly in the electrostatic field. It demonstrably enhances the elfectiveness of the antenna.

While I have illustrated and described one particular embodiment of my invention it will be understood that it may be constructed in various ways within the contemplation of my invention and under the scope of the following claims. a

I claim:

1. A magnetic radio receiving antenna device comprising a flat plate of magnetizable metal, a pair of permanent bar magnets laid against and secured to the plate with like poles thereof in confronting relation but separated from each other, a fiat coil of wire overlying the magnets and secured thereto in a plane parallel with the planes of the metal plate and the magnets and with its center positioned over the space between the magnets and with the axes of the magnets extending diametrically of the coil, the coil of wire having two terminals, and a lead wire attached to each terminal.

2. A magnetic radio receiving antenna as defined in claim 1 in which the area of the coil is less than the area of the plate, and the plate extends beyond the periphery of the coil in every direction in the plane of the plate.

References Cited in the file of this patent UNITED STATES PATENTS 1,710,085 Cooper Apr. 23, 1929 the coil may be connected to a ground wire or to a (Other references on following page) UNITED STATES PATENTS Polydoroif Jan. 11, 1944 Sontheimer May 8, 1945 Walsh; Mar. 1 8; 1947 Hansel -Ju1 4, 1950 Polydbrofi. Dec. 30, 1952 Germany June 25, 1953 

